The present invention relates to a piezoelectric single crystal device. In particular, it relates to a piezoelectric single crystal device capable of exhibiting piezoelectric properties with high sensitivity, even when used at temperatures higher than room temperature, specifically, within a specific high-temperature range of Trt° C. to (Trt−20)° C. (for example, about 50° C. to 70° C.) where Trt represents a transformation temperature (may be referred to as a phase transition temperature) between a pseudocubic system and a tetragonal system.
A piezoelectric single crystal device makes the conversion between electric energy and mechanical energy possible, and is widely used for applications such as, for example, accurate positioning actuators of magnetic heads, piezoelectric gyro devices, image stabilizers of digital still cameras, and cardiac pacemaker sensors.
The above-described piezoelectric single crystal device, including a solid solution of [Pb(Mg,Nb)O3](1-X)·[PbTiO3](X) (referred to as PMN-PT or PMNT) made of lead magnesium niobate and lead titanate and serving as a material for the single crystal has been previously known.
For example, U.S. Pat. No. 5,998,910 discloses a transducer having a composition represented by Pb(Mg1/3Nb2/3)1-yTiyO3, that includes a single crystal exhibiting excellent piezoelectric properties in a <001> direction of a pseudocubic system, and capable of exhibiting piezoelectric properties with high sensitivity.
The piezoelectric properties of the piezoelectric single crystal device can be evaluated based on values of the specific inductive capacity εr and the piezoelectric constant d33, and increases in these values generally indicate improvements of the piezoelectric properties of the single crystal device. The specific inductive capacity εr and the piezoelectric constant d33 vary depending on temperatures. However, these parameters are in a proportional relationship when the temperature is constant.
A piezoelectric single crystal device having a composition made of lead magnesium niobate and lead titanate exhibits excellent piezoelectric properties within a specific high-temperature range of Trt° C. to (Trt−20)° C. (for example, about 50° C. to 70° C.) as compared with the piezoelectric properties at room temperature.
Therefore, in the case where the piezoelectric single crystal device has the above-described composition, using the single crystal device within the specific high-temperature range described above (for example, about 50° C. to 70° C.), is advantageous to exhibit excellent piezoelectric properties.
However, the transducer described in U.S. Pat. No. 5,998,910 exhibits a specific inductive capacity in the order of 13,000 even at the maximum within the above-described specific high-temperature range and a small specific inductive capacity at room temperature (about 30° C.) of less than 5,000.